Melt-processed material with high cellulose fiber content

ABSTRACT

The present invention relates to a product comprising cellulose fibers wherein the cellulose fibers are at least partly modified to contain dialcohol cellulose and a melt-processing method of preparing the same.

FIELD OF THE INVENTION

The present invention relates to melt-processed products of dialcoholcellulose and a method of preparing the products. The present inventionfacilitates the preparation of extruded and/or injection molded productshaving high cellulose content.

BACKGROUND

Cellulose is probably the most abundant biopolymer on. Earth, and it isconsidered to be an important component in a future, sustainable andbio-based economy.

A problem with cellulose is the difficulty of processing the cellulosefor example by various melt-processing techniques. Extrusion andinjection molding of cellulose and especially cellulose fibers requiresa high content of a second thermoplastic polymer to facilitate theprocess. These composites or mixtures of cellulose and a second polymerhave, however, shown to suffer from pullout and debonding between thecellulose fibers and the second polymer, as well as formation ofagglomerates.

Bengtsson et al. (Composites: Part A, 38 (2007), 1922-1931) disclose acellulose fiber reinforced polypropylene composite with up to 60% ofcellulose fibers. The composite was prepared by extrusion by preparingpellets of the cellulose before compounding it with the polypropylene.

US2007/0004826 discloses a composition of cellulose ether, a plasticizerand a defoamer where the composition may be used in extrusion ofinorganic compositions.

Larsson et al. (Green Chemistry, 18 (2016), 3324-3333) andPCTSE2016/050663 describe a way of preparing dialcohol cellulose bypartly oxidizing the cellulose fibers (to dialdehyde cellulose) followedby a complete reduction of the formed aldehydes, forming dialcoholcellulose. The obtained material was used to prepare a material byconventional papermaking techniques.

Still there is no disclosure of melt-processinghigh-cellulose-containing material, for example by extrusion orinjection molding.

SUMMARY OF THE INVENTION

The object of the present invention is to overcome the drawbacks of theprior art by providing a cellulose-fiber-containing product where thecellulose has been at least partly modified to dialcohol cellulose.

The main aspect of the present invention relates to a product accordingto claim 1.

In a second aspect the present invention relates to a method ofpreparing the product according to the present invention wherein themethod comprises

-   -   a) providing a material comprising cellulose fibers wherein the        cellulose fibers are at least partly modified to contain        dialcohol cellulose and wherein the amount of the modified        cellulose fibers in the melt-processed product is more than 60        wt %; and    -   wherein the degree of conversion of the at least partly modified        cellulose to dialcohol cellulose, based on the total number of        oxidizable C2-C3 bonds in the cellulose material, is at least        10%;    -   b) optionally letting the material sorb moisture or water for a        sufficient period of time or until sufficient amount of water or        moisture have been sorbed; and    -   c) melt-processing the material into the product.

In a third aspect, the present invention relates to a materialcomprising cellulose fibers wherein the cellulose fibers are at leastpartly modified into dialcohol cellulose and wherein the amount of themodified cellulose fibers in the material is more than 60 wt %;

wherein the degree of conversion of the at least partly modifiedcellulose to dialcohol cellulose, based on the total number ofoxidizable C2-C3 bonds in the cellulose material, is at least 10%;

and wherein the material optionally has absorbed 5-40 wt % moisture orwater.

In a fourth aspect, the present invention relates to a method of meltprocessing a cellulose-fiber-containing product wherein the methodcomprises:

-   -   a) providing a material comprising modified cellulose fibers        wherein the modified cellulose fibers are at least partly        modified into dialcohol cellulose;    -   b) letting the material sorb moisture or water for a sufficient        period of time or until sufficient amount of water or moisture        have been sorbed; and    -   c) melt processing the material into a product.

In a fifth aspect the present invention relates to the use of theproduct as gas barrier, such as oxygen and/or water vapor barrier.

In a sixth aspect the present invention relates to the use of theproduct as a liquid barrier such as water barrier.

In a seventh aspect the present invention relates to a materialcomprising cellulose fibers wherein the cellulose fibers are at leastpartly modified into dialcohol cellulose and wherein the material haveabsorbed 5-40 wt % moisture or water.

All the embodiments disclosed herein relates to all the aspects unlessstated otherwise.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1, schematic reaction scheme of the modification of cellulose intodialcohol cellulose.

FIG. 2, Dynamical mechanical thermal analysis (DMTA) measurementsdisclosing apparent glass transition temperature at various relativehumidity conditions.

DETAILED DESCRIPTION OF THE INVENTION

In the present application the terms “sorb” or “sorption” encompassesboth adsorption and absorption.

In the present application the term “cellulose” also encompasseshemicellulose unless stated otherwise.

In the present application the term “melt-process” denotes a processwhere the temperature is high enough to cause the processed material toflow in a similar way to molten thermoplastics.

The present invention aims at providing melt-processed products ofcellulose or cellulose-containing material, and thereby the amount offossil-derived plastics may be reduced. It is well known that celluloseis very hard to mold or shape, for example through extrusion orinjection molding, into a product. The skilled person knows thatpolymeric material soften by moisture uptake or at elevated temperature,however he also knows that it is not the same thing as being meltprocessable. In order to overcome this problem a common way has been touse a mixture of cellulose and another thermoplastic polymer. Thepresent invention facilitates the preparation of products comprising upto 100% of cellulosic fiber material and there is no need to add anyadditive such as plasticizer during the processing.

Cellulose is a polysaccharide found in the primary cell wall of plantsand cellulose and cellulose derivatives may be found in a variety ofdifferent products such as paper, paper board, textiles, implants andgunpowder. The cellulose of the present invention may be oflignocellulosic origin such as from wood.

The cellulose fibers used when preparing the material and productaccording to the present invention may have but is not limited to anaverage diameter of at least 1 μm such as at least 5 μm, or at least 8μm, or at least 12 μm. The average length of the fibers is preferably atleast 0.3 mm, such as 0.3-4 mm.

It needs to be emphasized that there is a major difference betweencellulose fibers and fibrils or nanofibrils. Fibrils have a diameter ofa few nanometers while fibers are in the micrometer range i.e. fibersare thousand times bigger. Therefore many properties that fibrilsexhibit are not seen for fibers.

The cellulose may be any suitable cellulose such as cellulose obtainedfrom pulping. In one embodiment the cellulose is obtained from the Kraftprocess. In another embodiment the cellulose is obtained from bleachedpulp from the Kraft process. The cellulose obtained from a pulpingprocess usually also contains hemicellulose. However, the hemicellulosewill also undergo the modification as or similarly as described herein.

The Melt-Processed Product

The product according to the present invention is a molded or castproduct obtained by a melt-process which may be selected from but is notlimited to injection molding, extrusion, extrusion casting, extrusioninjection molding, extrusion coating or extrusion compression molding.The material used in the present invention is extrudable, whichfacilitates preparation of products having a more complex profile orcross-section by extrusion or injection molding or a combination ofmelt-processing operations, of the cellulose-containing material.

By modifying the cellulose fibers partly into dialcohol cellulose thecellulose containing material will be more easily melt-processed. Themodification into dialcohol cellulose may be done in two steps where thefirst step is oxidizing the cellulose on/in the fibrils constituting thecellulose fiber to dialdehyde cellulose to a desired extent. This ismainly a heterogeneous reaction performed in a fiber suspension. Apreferred oxidation agent is a periodate such as sodium periodate. Thedialdehyde groups on the cellulose are then reduced to dialcoholcellulose, for example by using a hydride such as a boron hydride, forexample sodium borohydride.

The modification of oxidizable C2-C3 bonds of the glucose monomer unitsof the cellulose molecules takes place firstly at the surface of thecellulose nanofibrils constituting the fibers. As the modificationproceeds, it is believed that the modified nanofibrils obtain acore-shell structure, and thereby, from the dialcohol shell, getmechanical and physical properties that resemble the properties ofthermoplastic polymers, which are advantageous in the processes ofextrusion and injection molding.

The oxidation time depends partly on the oxidation agent, theconcentration of the same, as well as the cellulose concentration andthe temperature where higher concentration and higher temperaturedecreases the oxidation time. As a non-limiting example the oxidationtime may be 0.1-40 hours such as 1-35 hours, 10-30 hours, or 20-25hours. In one embodiment the oxidation time is 0.5-4 hours such as 1-2hours. The oxidation temperature may be but is not limited to 20-60° C.,such as 30-50° C. However, longer oxidation time results in a higherdegree of modification which in turn may make the material moresusceptible to discoloration during the melt-processing step.

When determining the degree of modification or conversion of thecellulose into dialcohol cellulose the first step is to determine thedegree of conversion into dialdehydes. This is done by using the method“carbonyl content determination” described below. The conversion isgiven as a percentage of the maximum amount of conversion assuming purecellulose as starting material. In the second step all the aldehydes areassumed to be converted into alcohols (which also can be supported by asecond carbonyl content determination) unless there is any indication ordescription stating the opposite.

The degree of conversion of cellulose to dialdehyde cellulose prior toreduction to dialcohol cellulose is preferably above 13%, such as above18% or above 20%, based on the total number of oxidizable C2-C3 bonds inthe natural cellulose material. Further, the degree of conversion may bebelow 60%, such as below 50%. In one embodiment, the degree ofconversion to dialdehyde cellulose is between 22% and 49%, such asbetween 24% and 45%. The degree of modification or conversion of thecellulose fibers into dialcohol cellulose may be at least 10%, or atleast 20%, or at least 30%, or at least 32%, or at least 40%, or atleast 50%, or at least 60%, preferably less than 100%, or less than 90%,or less than 80% or less than 70%. In one embodiment the degree ofmodification is 30-60% such as 32-40% or 40-50%.

As the degree of conversion to dialcohol cellulose approach 100%, thecellulose will be dissolved and partly or fully take a non-fibrous form.This state is possible to work with but less desirable, since itrequires that the cellulose is re-flocculated into solid cellulosematerial, which is a non-trivial extra process step. When solidifiedfrom solution, the cellulose will be more in the form of a powder thanfibers. From a process point of view, the optimal degree of conversionof the cellulose appears to be at from 25 to 60% such as 35-50%.

The fiber suspension used in the method for preparing the fibers of thematerial may be a suspension of beaten fibers.

The amount of the modified cellulose fibers in the product may be 1-100wt %. In one embodiment the amount is 10 wt % or more, or 20 wt % ormore, or 30 wt % or more, 40 wt % or more, or 50 wt % or more, or 60 wt% or more, or 61 wt % or more, or 63 wt % or more, or 65 wt % or more,or 70 wt % or more, or 75 wt % or more, or 80 wt % or more, or 85 wt %more, or 90 wt % or more, or 95 wt % or more, or 100 wt %.

When the amount of modified cellulose fiber is less than 100 wt % theproduct may further contain at least one second polymer which may be athermoplastic polymer and may be selected from a natural polymer, anatural polymer derivative, a polyolefin, a polyethylene vinyl alcoholco-polymer, a polyester, polyurethane, epoxy resin, a polyacrylic acid,a poly(meth)acrylic acid or a polyamide, or a mixture or a co-polymer oftwo or more of any said polymers. In one embodiment one of the secondpolymers is a thermoset. In one embodiment the thermoset is selectedfrom polyester, polyurethane and epoxy resin. In one embodiment one ofthe second polymers is polyethylene or polypropylene. In anotherembodiment one of the second polymers is natural cellulose, hemicellulose or starch, or a derivative of natural cellulose, hemicellulose or starch. In another embodiment one of the second polymers isnatural cellulose. In another embodiment one of the second polymers iscellulose derivative. In another embodiment one of the second polymersis a co-polymer of a polyolefin and an acrylic or methacrylic acid. Inanother embodiment one of the second polymers is poly(ethylene acryclicacid) (EAA). In another embodiment one of the second polymers ispolyethylene methacrylic acid. In another embodiment one of the secondpolymers is polyethylene terephthalate (PET). In one embodiment one ofthe second polymers is poly(butylene terephthalate) (PBT). In oneembodiment one of the second polymers is poly(ether ether ketone)(PEEK). In one embodiment one of the second polymers is a Nylon(polyamide) such as Nylon 11, Nylon 12, Nylon 6 or Nylon 66. In oneembodiment one of the second polymers is a biodegradable polyester suchas polycaprolactone, poly lactic acid or polyglycolic acid. In oneembodiment the product contains two or more second polymers.

The total amount of the second polymers may be 1-99 wt %. In oneembodiment the total amount of the second polymers is 10 wt % or more,or 20 wt % or more, or 30 wt % or more, 40 wt % or more, or 50 wt % ormore. In another embodiment the total amount of the second polymer ismore than 1 wt % but less than 40 wt %, or less than 35 wt %, or lessthan 30 wt %, or less than 25 wt %. In another embodiment the totalamount of the second polymer is 10-50 wt % such as 39-12 wt %, or 35-15wt %, or 20-30 wt %.

The product may further contain any suitable additive such as aplasticizer, cross linking agent, reinforcement fibers, compatibilizer,fillers, defoamer or pigment. In one embodiment the product comprises across linking agent such as a polyol, polyaldehydes, polycarboxylicacid, polyamine, isocynate, 2,2′-azobis(2-methylpropionnitrile) (AIBN),urea, formal aldehyde and bisphenol A. The reinforcement fibers may beselected from glass fiber or carbon fiber. In one embodiment the productcomprises a filler such as a mineral filler. However the product mayalso be essentially free from any additive. In one embodiment theproduct is essentially free from any plasticizer and compatibilzer. Inone embodiment the product is essentially free from any cross-linkingagents. In one embodiment the amount of additive is 0.5 to 10 wt %. Inone embodiment the amount is less than 8 wt %, or less than 6 wt %, orless than 4 wt %, or less than 2 wt % but preferably at least 1 wt %.

The product may be a cap, closure, closure device, package top, opening,toy, container, construction part, interior decoration or an automotivepart. Automotive parts may be interior or under hood parts, structuralparts and non-load bearing applications. As construction part orinterior decoration the product may be used as a profile, strip, edgingor skirting-board.

The mechanical properties may be tailored by varying the type and amountof the second polymer and/or by changing the degree of modification. Forexample by increasing the content of the modified cellulose when mixedwith a soft polymer, such as EAA, the obtained material showed anincrease in the elastic modulus and the yield strength significantly.

Without being bound by theory it is believed that the modification ofthe fibers according to the present invention will increase thedispersity of the fibers when mixed with a second polymer leading toreduced number of fiber pullouts or debonding i.e. the matrix does notadhere properly to the fiber.

The products have good gas barrier properties such as oxygen and/orwater vapor, barrier properties. It may also function as a liquidbarrier for example for beverages, liquid food, oils, shampoos, soap orwater etc. The material is less sensitive to degradation from themoisture and could be used as extruded layers in a laminate for liquidpackaging. Further, when a second polymer is used the strong interactionbetween the two different polymers is also believed to be beneficial forthe barrier properties.

The product discloses water vapor permeability and oxygen permeabilityproperties as shown in the examples confirming its suitability as abarrier. The water vapor permeability (g*mm/m²*kPa*24 h) according toASTM F1249-06, measured at a relative humidity (RH) of 50% and atemperature of 23° C., may be 100 or lower, or 80 or lower, or 50 orlower, or 30 or lower, or 10 or lower. The oxygen permeability(g*μm/m²*kPa*24 h) according to ASTM D3985, measured at a relativehumidity of 50% and a temperature of 23° C., may be 200 or lower, or 150or lower, or 100 or lower, or 50 or lower. The present invention alsoprovides products having low oxygen transmission rate (OTR). It wasunexpected that the melt processed, injection molded, products exhibitedsuch good mechanical and barrier properties since these processes tendto break down the fibers.

The barrier properties of the product make it suitable when employed inpackaging applications, such as extrusion coated layers and moldedopening devices, closures and caps.

The Method of Melt-Processing

The modification of the cellulose fibers may be done according themethod described in PCTSE2016/050663 which is hereby incorporated byreference.

The material to be melt-processed comprises modified cellulose fibersand optionally one or more second polymer. The modified cellulose may beprovided in any suitable form such as paper, a powder, particles orpellets. Any mixing of the modified cellulose with a second polymer maybe done in any suitable way. According to an embodiment, the modifiedcellulose may be compounded with a thermoplastic polymer as amasterbatch compound, for example in the form of particles or pellets.

The material may then be allowed to sorb moisture or water. The sorptionmay be done by leaving the material in a moisture-containing environmentfor a sufficient period of time, until sufficient amount of moisture orwater has been sorbed by the material. The moisture containingenvironment may be a container with steam. The material may also sorbwater by adding water to the material or by submerging the material intowater for a sufficient period of time. Cellulose will sorb less moistureor water if the temperature during the sorption is increased andtherefore the temperatures should not be increased too much. In oneembodiment the sorption is done at 30° C. or lower such as at roomtemperature. The relative humidity (RH) during the adsorption may be30-100% such as 50-99% or 70-95%. The material may be left in themoisture-containing environment for at least 5 minutes, or at least 15minutes, or at least 30 minutes or at least 1 hour, or at least 2 hours.The material may be dipped in water or submerged in the water. In oneembodiment the material is dipped or submerged in water for at least 10seconds or at least 30 seconds, or at least 1 minute. In anotherembodiment the material is dipped or submerged for 1-10 seconds. Thesorption time is partly dependent on the amount of material and themethod of adding moisture or water. In one embodiment the material istreated in the moisture-containing environment having a relativehumidity of 70-100% for at least 10 minutes. The moisture content of thematerial after this step may be 5-40 wt % such as 10-30 wt %.

By allowing the material to sorb moisture, the material may be moreeasily melt-processed since lower temperature and less force is needed.Furthermore the sorption is believed to inhibit discoloration duringprocessing since the processing temperature may be lowered. A materialthat is not allowed to sorb moisture should preferably have a highdegree of modification in order to facilitate the melt-processing ofhigh-cellulose-content material. For example, dry processing (i.e.material that has not been allowed to sorb any moisture of water) at acellulose content of at least 70% would preferably have a degree ofmodification of at least 30%, or at least 40%, or at least 50%, or atleast 60% but preferably less than 95%, or less than 90%, or less than80% or less than 70%. In one embodiment the degree of modification is30-60% such as 40-50%. The material may have a high degree ofmodification as well as have been allowed to sorb moisture. The use andamount of a second polymer may also affect the melt processingproperties.

The material may then be compounded or melt-processed at 60-200° C.,depending on the properties of the material, using any suitabletechnique such as a melt-screw extruder or a twin-screw extruder. Duringthe compounding or melt-processing the temperature may be high enough inorder to make the material flow. The compounding or melt-processing maybe described as a melt process where the temperature is high enough tomelt or impart the material with a melt-like state, or make it softenough to make it flow. For compounding of material that has beenallowed to sorb moisture, a lower temperature may be used such 60-100°C. or 70-90° C. For dry material, i.e. material that has not beenallowed to sorb moisture or water, a temperature of 120-160° C. may beused such as 130-150° C. Compounding of the material may be done during5-10 minutes. Lower temperatures are sometimes more preferred since itreduces the risk of discoloration.

The material is melt-processed, for example, through injection molding,extrusion, extrusion casting, extrusion injection molding, extrusioncompression molding or extrusion coating. In one embodiment the productis melt-processed by extrusion and/or injection molding.

In one embodiment the product is prepared by first compounding thematerial. The compounded material is then converted into particles orgranules of suitable size, for example by cutting or grinding. Thegranules are then extruded using an extrusion screw and pressed througha nozzle and into a mold or into a strand or a film.

By extruding a film of the material onto a cooling roller or onto asubstrate which is arranged on a roller extruded films or coatedsubstrates may be prepared. Extrusion cast films may be stretched in anydirection in order to align the fibers or the polymeric chains, for thepurpose of improving various properties, such as mechanical properties,of the films.

When the material is injection molded it may first be compounded in aseparate extruder or it may be added to the injection molding apparatusdirectly optionally together with the optional second polymer and theoptional additives. The injection molding may be one step in aproduction line where the product is injection molded directly intoplace, so called in-line injection molding.

The melt-processing is done at a temperature suitable for the specificmaterial composition, depending on the glass transition temperaturesand/or the melting temperature. For example injection molding may bedone at a temperature of 100-150° C. such as 120-130° C. for a materialcomprising modified cellulose fibers and poly(ethylene acrylic acid). Ifthe cellulose has an increased moisture content, the temperature can belowered.

The material to be processed may further contain any suitable additivesuch as a plasticizer, cross-linking agent, compatibilizer, filler,defoamer or pigment. However the material may also be essentially freefrom any additive. In one embodiment the material is essentially freefrom any plasticizer besides from optional water or moisture from thesorption step. In another embodiment the material is essentially freefrom any compatibilzer. In one embodiment the product is essentiallyfree from any cross-linking agents.

EXAMPLES Example 1

Fibres

Dried bleached kraft fibers (K46) were provided by SCA AB (Ostrand pulpmill, Sweden). Before use, the fibers were soaked in water anddisintegrated and then mechanically beaten in a Voith mill to an energyinput of 160 Wh/kg (about 30 SR).

Chemicals Sodium (meta)periodate for the oxidation of cellulose,isopropanol (99.8% purity) used as radical scavenger and hydroxylaminehydrochloride for the determination of the degree of oxidation. Sodiumborohydride was used to reduce dialdehyde cellulose to dialcoholcellulose. These and all other chemicals, such as hydrochloric acid andsodium hydroxide, were all of analytical grade.

Oxidation of cellulose Under stirring, 5.4 gram of sodium periodate pergram of fiber was added to a 4 g/l fiber suspension containing 6.3%isopropanol (by volume) as radical scavenger to prevent side reactionsand chain scission. To further prevent chain scission, the oxidationreactions were performed in the dark for 16 h, 24 h or 32 h before thereaction was terminated by filtration and thorough washing withdeionized water. The degree of conversion to dialdehyde cellulose,assuming pure cellulose as starting material, was determined to be 32%,46% and 55% (hereafter called Fiber32, Fiber46 and Fiber55),respectively, by reaction with hydroxylamine hydrochloride and titrationwith sodium hydroxide according to an earlier described procedure.

Reduction of Cellulose

The fibers were then suspended to 4 g/l and the dialdehyde celluloseformed was reduced to dialcohol cellulose by adding 0.5 g sodiumborohydride per gram of fibers. To limit the pH increase to about pH 10upon addition of sodium borohydride, monobasic sodium phosphate wasadded together with the borohydride in an amount corresponding to 0.01M. The reduction time was kept constant at 4 h (analysis shows nomeasurable content of remaining aldehydes after this time), followed byfiltration and thorough washing.

Paper Preparation

Handsheets with an approximate grammage of 150 g m⁻² were prepared usingtap water in a Rapid Kothen sheet former (Paper Testing Instruments,Austria). The sheets were dried at 93° C. under a reduced pressure of 95kPa. The sheets were then stored at 23° C. and 50% RH until furthertesting/use.

Example 2

In order to test the effect of scale-up of the modification and to haveenough material for longer test series, the following experimental setup was used:

The modification was done as described in Example 1 but instead of a drycontent of 0.4% it was increased to 4%, the amount of oxidation agentwas reduced to 1,4 g (NaIO₄)/g fiber and the temperature was raised to50° C. in order to reduce the reaction time to 3-4 hours. The degree ofoxidation was determined by carbonyl content analysis to be 38% (thesefibers are hereafter called Fiber38).

During the reduction step the amount of reducing agent was reduced from0.5 g/g fiber to 0.2 g/g fiber (full reduction of aldehydes was measuredby carbonyl content determination).

Example 3

In order to obtain a greater understanding of the hygro- andthermo-mechanical properties of the modified cellulose, dynamicalmechanical thermal analysis (DMTA) was conducted over a select number ofrelative humidities. All DMTA tests were conducted under controlledenvironment utilizing a Q800 DMTA from TA Instruments with a moisture-and temperature-controlled chamber. Approximately constant relativehumidity (±2.5% at all data points in this manuscript except for theDMTA results at 113° C. and high humidity, which have a maximum ±12%error in humidity) was maintained during each test (0%, 50%, 60%, and70% RH). The desired relative humidity and a temperature of 10° C. wasachieved and then maintained over the first 120 min of the test. After120 min had passed, the temperature was swept from 10 to 113° C. for 206min, held at 113° C. for 30 min, swept from 113 to 10° C. for 206 min,and then held at 10° C. for 30 min. This temperature cycle was conductedthree times or until the sample failed. Various output parameters wereobtained, including relative humidity near the surface of the sample,storage modulus, and loss modulus. The data from the first temperaturecycle was not utilized due to hysteresis effects (i.e. the first andsubsequent cycles showed slightly different results). Therefore, onlythe second and subsequent cycles were utilized in the data analysis. Thepeaks in loss modulus during the temperature sweeps were defined as theapparent glass transition temperature.

The results are disclosed in FIG. 2.

Example 4

Processing conditions of dialcohol-cellulose-fiber (hereafter calledfiberX, where X denotes the degree of modification)-based composites.

Instruments:

DSM Micro compounder 5 ml: MC 5 (DSM, Xplore Instruments BV, TheNetherlands) Thermo Scientific HAAKE MiniJet Pro—Thermo FisherScientific

Cellulose Fiber and EAA Assisted Processing:

Material obtained in Example 1 and 2 were used to prepare injectionmolded products. Composites with different fiber and EAA content wereprepared as well as 100% fiber product. The different contents are seenin tables 1 to 4.

Compounding

T=120° C.

v=30 or 60 rpm

t=5 min

Injection

T=120-140° C.

Pi=1000 bar

t=≈10 min

The force required during the compounding (extrusion) for the differentmaterials is shown in table 1, 2 and 5.

DMTA testing was conducted according to by ASTM D882: Alpha transitiontemperatures (Ta) as peak value of loss modulus (E″); Damping factor aspeak value of tan delta; Storage Modulus (E′) at −20° C. and at 25° C.(RT).

TABLE 1 Table over force needed during injection molding of materialcontaining different amounts (10-90 wt %) of dialcohol cellulose. SAMPLEFORCE [N] EAA 60 rpm 1500 10% Fiber 38/EAA 60 rpm 1700 30% Fiber 38/EAA60 rpm 2100 50% Fiber 38/EAA 60 rpm 2600 70% Fiber 38/EAA 60 rpm 400090% Fiber 38/EAA 30 rpm 4800

TABLE 2 Table over force needed during compounding (extrusion) ofmaterial containing 70 wt % of dialcoho lcellulose with increasingdegree of conversion to dialcohol cellulose. SAMPLE FORCE [N] EAA 150070% Fiber 32/EAA 30 rpm 4100 70% Fiber 46/EAA 60 rpm 3100 70% Fiber55/EAA 60 rpm 2600

TABLE 3 Table over mechanical properties of materials containingdifferent amounts of dialcohol cellulose. Damping E′ at −20° C. E′ at RTfactor Tα SAMPLE [MPa] [MPa] [° C.] [° C.] EAA 1530 220 27.7 8.8 60 rpm10% Fiber 38/EAA 2030 520 28.5 9.8 60 rpm 30% Fiber 38/EAA 2810 987 29.714.5 60 rpm 50% Fiber 38/EAA 3900 1800 42.4 19.1 60 rpm 70% Fiber 38/EAA6790 3190 51.0 22.2 60 rpm 90% Fiber 38/EAA 9170 4370 68.4 27.1 30 rpm

TABLE 4 Table over mechanical properties of materials containingdifferent amounts of dialcohol cellulose. E_(Young) σ_(yield) Γ_(break)ε_(break) Energy_(break) SAMPLE [MPa] [MPa] [MPa] [%] [Jg⁻¹] EAA 110 2.710.6 174.6 5.50 60 rpm 10% Fiber 38/EAA 60 380 4.3 12.5 56.3 1.71 rpm30% Fiber 38/EAA 60 980 8.4 12.7 27.4 1.11 rpm 50% Fiber 38/EAA 60 190014.3 19.2 7.2 0.31 rpm 70% Fiber 38/EAA 60 3210 19.0 24.2 5.3 0.25 rpm

H₂O Assistance:

100% fiber, 38% (Fiber 38) and 55% (Fiber 55) conversion to dialcoholcellulose, conditioned till constant moisture content at RH>90%

Compounding

T=80° C.

v=60 rpm

t=5 min

Injection

T=120-140° C.

Pi=1000 bar

t=≈10 min

The materials were either extruded (compounded) dry or wet (RH90%) at120° C. or 80° C. at 30 or 60 rpm and injected. The injected sampleswere then dried at 105° C. for 2 hours. The stress-strain measurementswere conducted using an Instron 5944 at 23° C. and 50% RH.

TABLE 5 Table over force needed during compounding (extrusion) ofmaterial containing 100 wt % of Fiber 55- dry and wet samples and wetFiber 38. SAMPLE FORCE [N] 100% Fiber 55 dried 120° C. 30 rpm 4900 100%Fiber 55 RH > 90% 80° C. 60 rpm 1500 100% Fiber 38 RH > 90% 80° C. 60rpm 2000

TABLE 6 Tensile test for 100% Fiber 55 - dry and wet samples. E_(Young)σ_(yield) σ_(break) ε_(break) SAMPLE [GPa] [MPa] [MPa] [%] 100% Fiber 55dried 10.2 — 13.1 0.2 120° C. 30 rpm 100% Fiber 55 12.2 — 5.5 0.1RH >90% 80° C. 60 rpm

As seen above, high cellulose fiber content material may be extruded andinjection molded at a reasonable temperature without the addition of anyadditive such as plasticizer or compatibilizer. Furthermore, theobtained material also has good mechanical properties.

Example 5

Dense cellulose is known to be a good oxygen barrier, but not as goodwater vapor barrier. To assess the barrier properties of themelt-processed material, pieces of injection-molded material washot-pressed between two smooth surfaces at a pressure in the approximaterange of 15-50 MPa and further conditions according to table 5. Thefilms formed were then masked using custom-designed, double-adhesive,aluminum foil masks and oxygen and water vapor transmittance wasmeasured at 50% RH using a Mocon MOCON OX-TRAN® 2/21 and MOCONPermaTran—W 3/33, respectively. The material used was Fiber38. The testarea was 2.5 cm². The results are shown in table 7.

TABLE 7 Measurements of barrier properties of 100 wt % modifiedcellulose (100 Fiber38) and materials of modified cellulose (Fiber38)and a second polymer (EAA or polyvinyl alcohol (PVA)) in differentratios. WVRT is Water Vapor Transmission Rate and OTR is OxygenTransmission Rate. Hotpressing Thickness O2 Material (temp, time) (um)OTR¹ permeability² WVTR³ Vapor permability⁴ 100 Fiber38 150° C., 5 + 2min 383 10 38 4.4 1.2 50/50 90° C., 2.5 min 437 268 83 Fiber38/EAA 50/5090° C., 2.5 min 326 94 22 Fiber38/EAA 70/30 150° C., 5 min 465 1966 650Fiber38/PVA 70/30 150° C., 5 min 756 11 82 171 92 Fiber38/PVA 70/30 90°C., 3 min 250 46 113 Fiber38/EAA 70/30 90° C., 3 min 332 115 377Fiber38/EAA ¹(ml/(m2 * 24 h) ²(ml * um/(m2 * kPa * 24 h)) ASTM D3985³(g/(m2 * 24 h) ⁴(g * mm/(m2 * kPa * 24 h))

Example 6

A pilot production of the modified cellulose fiber material wasperformed by RISE Processum AB.

Pulp (39 kg, 4.5% of dry content) was added to a 50 liter stainlesssteel reactor with a mechanical stirrer and heated to 51° C. 2.5 literof isopropanol was added followed by 2.5 kg of sodium periodate. Thereaction mixture was stirred during 105 minutes. The reactor was emptiedat the bottom and was filtered (FSI filter size 2) and was quicklywashed with deionized water in order to lower the temperature and toremove the excess of periodate. The pulp or product was washed withdeionized water until the wash water had a conductivity of less than 10μS/cm.

The product was suspended in water and 7.5 kg of ice to a total weightof 37 kg. The cooled product was placed in the reactor and NaBH₄ (350 gin around 2 liter of water) was added during 3 minutes. The temperaturewas monitored to avoid temperature above 10° C. Stirring was continuedfor 1 hour and the reaction product was emptied from the bottom of thereactor. The reaction product was filtered using filter bags (FSI filtersize 2) and was quickly washed with deionized water to remove remainingNaBH₄. The product was washed until the wash water conductivity was lessthan 10 μS/cm.

The filtered and washed product was dewatered using a mechanical screwpress to a dry content of 10-15%.

The carbonyl content after the oxidation step was determined to be 5.2mmol/g and the total yield was 48.5%.

Example 7

Caps of the material obtained from Example 6 were prepare and measuredconcerning melt flow index and OTR (Oxygen Transmission Rate). Theresults are shown in Table 8 and 9.

The caps (80 wt % modified cellulose and 20 wt % EAA) were injectionmolded using a BOY 12A from Dr Boy GmbH & Co. The injection molding wasdone at a pressure of 2200-2400 bar, at a temperature of 130° C. and atan injection speed of 14 ccm/sec.

Colored caps were also injection molded using 2-3 wt % of pigment.

TABLE 8 Melt flow index measurements of virgin fibers, MFC and modifiedcellulose/EAA (without pigment). Virgine cellulose Modified celluloseProperty fibers MFC* and 20 wt % EAA MFR.** Does not melt Does not melt5 g/min 190° C.-5 kg Melt flow was tested according to ISO 1133:1999*MFC is Microfibrillated cellulose **MFR—Melt flow ratio

OTR measurements were performed using the same instrument as describedabove. The samples for OTR measurements were glued with epoxy on to aspecial holder and measured at 3 different climates at an oxygen levelof 21%: 23° C. and 50% RH (21% 23° C./50% RH), 23° C. and 80% RH (21%23° C./80% RH) and 38° C. and 90% RH (21% 38° C./90% RH). Readings weretaken when OTR reached equilibrium. Commercially available caps of LDPE(Low Density Polyethylene) were used as reference. The given thicknessis the top, the edges are somewhat thicker (0.88 mm and 0.86 mm).

TABLE 9 Oxygen Transmission Rate measurements for sample of 0.8 mmthickness (average). The unit is cc/part/24 h Modified cellulose Climateand 20% EAA LDPE 21% O2 38° C./90% RH 0.016 0.184 21% O2 23° C. /80% RH0.001 0.078 21% O2 23° C. /50% RH 0.001 0.084

The caps showed very good OTR results which is unexpected since theinjection molding is quite a harsh method for the fibers.

Example 8

100 wt % of the modified cellulose fiber material (dry state) obtainedin Example 6 was melt extruded using a BOY 12A, from Dr Boy GmbH Co, ata temperature of 130° C., and a pressure of 2200-2400 bar.

1. A melt-processed product comprising cellulose fibers wherein thecellulose fibers are at least partly modified to contain dialcoholcellulose and wherein the amount of the modified cellulose fibers in themelt-processed product is more than 60 wt %; and wherein the degree ofconversion of the at least partly modified cellulose to dialcoholcellulose, based on the total number of oxidizable C2-C3 bonds in thecellulose material, is at least 10% but less than 70%.
 2. Themelt-processed product according to claim 1 wherein the amount of themodified cellulose fibers in the melt-processed product is 1 wt % ormore.
 3. The melt-processed product according to claim 1 wherein theamount of the modified cellulose fibers in the melt-processed product isless than 100 wt % and wherein the product further contains athermoplastic polymer.
 4. The melt-processed product according to claim3 wherein the product further contains a polyolefin wherein thepolyolefin is selected from polyethylene or polypropylene.
 5. Themelt-processed product according to claim 3 wherein the product furthercontains a natural polymer wherein the natural polymer is naturalcellulose, hemi cellulose or starch or a derivative of naturalcellulose, hemi cellulose or starch.
 6. The melt-processed productaccording to claim 1 wherein the degree of conversion of the at leastpartly modified cellulose to dialcohol cellulose, based on the totalnumber of oxidizable C2-C3 bonds in the cellulose material is at least20%.
 7. The melt-processed product according to claim 1 wherein theproduct is injection molded, extruded, extrusion cast, extrusioninjection molded, extrusion coated or extrusion compression molded. 8.The melt-processed product according to claim 1 wherein the product is acap, closure device, package top, openings, toy, container, constructionparts, interior decoration or automotive parts.
 9. The melt-processedproduct according to claim 1 wherein the product is injection molded orextruded and wherein the amount of modified cellulose fibers is at least70 wt %.
 10. A method of preparing the product according to claim 1wherein the method comprises a) providing a material comprisingcellulose fibers wherein the cellulose fibers are at least partlymodified to contain dialcohol cellulose and wherein the amount of themodified cellulose fibers in the melt-processed product is more than 60wt %; and wherein the degree of conversion of the at least partlymodified cellulose to dialcohol cellulose, based on the total number ofoxidizable C2-C3 bonds in the cellulose material, is at least 10% butless than 70%; b) optionally letting the material sorb moisture or waterfor a sufficient period of time or until sufficient amount of water ormoisture have been sorbed; c) melt-processing the material into theproduct; and wherein the modification of the cellulose fibers is done intwo steps where the first step is oxidizing the cellulose on/in thefibrils constituting the cellulose fibers to dialdehyde cellulose to adesired extent and then reducing the dialdehyde groups on the celluloseto dialcohol cellulose, and wherein the oxidation is mainly aheterogenous reaction performed in a fiber suspension.
 11. The methodaccording to claim 10 wherein the material is allowed to sorb moistureor water for a sufficient period of time or until sufficient amount ofwater or moisture have been sorbed prior to melt-processing thematerial.
 12. The method according to claim 10 wherein the degree ofconversion of the dialcohol cellulose is at least 20%.
 13. The methodaccording to claim 10 wherein the melt-processing is selected frominjection molding, extrusion, extrusion casting, extrusion coating,extrusion compression molding and extrusion injection molding.
 14. Themethod according to claim 13 wherein the melt-processing is injectionmolding and/or extrusion.
 15. The method according to claim 10 whereinmaterial is allowed to sorb moisture or water and wherein the injectionmolding or extrusion is done at a temperature of 60-100° C.
 16. Themethod according to claim 10 wherein the melt processing is done at atemperature of at least of at least 120° C.
 17. A material comprisingcellulose fibers wherein the cellulose fibers are at least partlymodified into dialcohol cellulose and wherein the amount of the modifiedcellulose fibers in the material is more than 60 wt %; wherein thedegree of conversion of the at least partly modified cellulose todialcohol cellulose, based on the total number of oxidizable C2-C3 bondsin the cellulose material, is at least 10% but less than 70%; andwherein the material optionally has absorbed 5-40 wt % moisture orwater. 18-19. (canceled)
 20. The melt-processed product according toclaim 1 wherein the amount of the modified cellulose fibers in themelt-processed product is 63 wt % or more.
 21. The melt-processedproduct according to claim 1 wherein the amount of the modifiedcellulose fibers in the melt-processed product is 65 wt % or more. 22.The melt-processed product according to claim 1 wherein the amount ofthe modified cellulose fibers in the melt-processed product is 75 wt %or more.
 23. The melt-processed product according to claim 1 wherein theamount of the modified cellulose fibers in the melt-processed product is90 wt % or more.
 24. The melt-processed product according to claim 1wherein the amount of the modified cellulose fibers in themelt-processed product is less than 100 wt % and wherein the productfurther contains a thermoplastic polymer wherein the thermoplasticpolymer is selected from natural polymer, a natural polymer derivative,a polyolefin, a polyethylene vinyl alcohol co-polymer a polyester, apolyacrylic acid or a polyamide, or a co-polymer or a mixture of two ormore of said polymers.
 25. The melt-processed product according claim 1wherein the degree of conversion of the at least partly modifiedcellulose to dialcohol cellulose, based on the total number ofoxidizable C2-C3 bonds in the cellulose material is at least 30%. 26.The melt-processed product according claim 1 wherein the degree ofconversion of the at least partly modified cellulose to dialcoholcellulose, based on the total number of oxidizable C2-C3 bonds in thecellulose material is from 32% to 40%.
 27. The method according to claim10 wherein the degree of conversion of the dialcohol cellulose is atleast 30%.